What Slartibartfast doesn't tell them, besides his favorite place to brunch on Sundays, is that the button makes the aircar go very fast.
Arthur and the others very soon find themselves at the Heart of Gold spaceship. Next to it is the policemen's spaceship, which seems totally dead, sort of like the policemen.
No one else is curious, but Ford (again) goes to check it out and discovers that the computer is dead and Marvin is lying face down on the ground nearby.
Marvin explains that he was talking to this new ship—until the ship committed suicide. That also explains why the police died.
(If you're keeping track, this makes the most dangerous things in this book: the Vogon fleet, Marvin's depression, and Vogon poetry. There's got to be a lesson here, but we can't figure out what it is.)